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IPV6 Addressing in Computer Network

Computer Network | IPv6 Addressing: In this tutorial, we will introduce you to IPV6 (Internet Protocol Version 6) Addressing along with the IPV6 Header and IPV6 Routing Protocols. By Mahima Rao Last updated : May 04, 2023

What is IPV6 Addressing?

The IPV6 address is 128 bits. Whereas IPV4 is represented by 4 groups of decimal numbers, same IPV6 is represented by 8 groups of hexadecimal numbers. The example of IPV6 address is 2001:0db8:85a3:0000:0000:8a2e:0370:7334.

As you are seeing the IPV6 address has been divided into 3 parts. Each part has different significance. Global prefix part network ID is used for routing. Its size is 48 bits. These are represented by the initial 3 groups.

The subnet field comes after the global prefix field, it contains a number that is used to identify the subnetwork. Its size is 16 bits. The Interface ID uniquely identifies any host. This ID identifies the host as unique and globally also. Its size is 64 bits.

You can also use shorthand expressions to write IPV6 addresses. For example, if you wish, you can also type the IPV6 address given above.


The groups in which all the zeros were represented on are represented by the single zero. You can do this with all the groups in which all the zeroes are present. When two such groups in which all the zeros come together, then you can replace them with a double colon as given below.


IPV6 Header Format

By looking at the IPV6 address, if you are thinking that the IPV6 header is very big and complicated, then it is not so. The designers of IPV6 have designed the IPV6 header in such a way that it should be the least field in which it performs as many tasks as possible. The IPV6 header contains 8 fields. Its size is 40 bytes.

This is a very simple header that you can easily understand.

The IPv6 header contains 8 fields. They are: Version, Class, Flow Label, Payload Length, Next Header, Hop Limit, Source Address, and Destination Address. All these fields are explained below:

1. Version

This field has value 6. This field defines the version of internet protocol. The size of this field is 4 bits.

2. Class

This field represents the traffic class. Its size is 8 bit. This field is similar to the Type of Service field of IPV4 header.

3. Flow Label

The size of this field is 24 bits. This field is used to mark packet and traffic flow. This field tells the sequence of packets that flow from source to destination.

4. Payload Length

This field stores the size of the data. The size of this field is not fixed.

5. Next Header

This field tells you what the next header will be. This feature is not available in IPV4.

6. Hop Limit

This field tells you how many hops (routers) IPv6 packets will cross before being destroyed.

7. Source Address

In this field, the source host's 128-bit IPV6 address is defined.

8. Destination Address

In this field, the destination host of 128-bit IPV6 address is stored.

IPV6 Routing Protocols

All the routing protocols you've read so far were not able to support all of IPV6. So some of them were abolished and some were upgraded to work with IPV6.

By upgrading the protocol, the techniques used for IPV4 routing protocols will also be used with IPV6. This will not help you to understand IPV6 routing.

As you know, broadcasting in IPV6 has been completely abolished. Therefore, protocols that use broadcasting cannot work with IPV6.

Mainly works with IPV6 3 routing protocols. In CCNA exams, you will only be asked about IPV6 static routing and OSPFv3. Let's now learn about these protocols. Static routing will be explained in the configuration part.

1. RIPng

The full name of RIPng is Routing Information Protocol Next Generation. This protocol is an upgraded version of the RIP used with IPV4, which has been upgraded to work with IPV6. This is an Interior Gateway Protocol that uses distance vector algorithm to determine the best route.

2. EIGRPv6

The EIGRP for IPV6 includes the same features that are available in the EIGRP version of IPV4. Also, most operations are performed in the same way as IPV4 performs in the EIGRP. But there are some differences in these versions as if EIGRPv6 is configured on straight router interfaces and if the router ID is not, then you can not configure EIGRPv6 etc.

3. OSPFv3

OSPFv3 is a link state routing protocol. This is an upgraded version of OSPF used with IPV4. It has been upgraded to work with IPV6. All of its basic features are the same as found in OSPF.

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